Mixed news from global miner Rio Tinto.It posted a stronger-than-expected eight percent rise in second-quarter output of iron ore, the material that accounts for the bulk of its profit. But at the same time Rio Tinto’s Chief Executive Tom Albanese warned world markets – particularly aluminium – remain tough. He added the firm would keep trying to hold down costs as well as align production with demand and reduce debt. And he said a recovery in Chinese steel demand is expected to continue into the second half of this year. Meanwhile a possible plan for Rio Tinto to merge its Australian coal mining business with that of BHP Billiton is being reported. The story in Australia’s Herald Sun newspaper said the two mining giants could see massive cost savings with such a merger but analysts pointed out strict competition laws in Europe could create obstacles.